A retrovirus showing characterizations of the etiological agent of AIDS has been identified. It was first described in an article of Barre-Sinoussi et al., Science, 220, 868 (1983).
This retrovirus has the following characteristics. It is T-lymphotropic; its preferred target is constituted by Leu 3 cells (or T4 lymphocytes); it has reverse transcriptase activity requiring the presence of Mg.sup.2+ and exhibits strong affinity for poly(adenylate-oligodeoxy-thynidylate) [poly(A)-oligo(dT) 12-18]; it has a density of 1.16-1.17 in a sucrose gradient, an average diameter of 139 nanometers; and a nucleus having an average diameter of 41 nanometers; the lysates of this virus are recognized immunologically, these lysates contain a protein p25 recognized by the same sera but which is not recognized immunologically by the p24 protein of the HTLVI and II viruses.
Retroviruses of this type (sometimes denoted by the generic abbreviation LAV) have been deposited in the National Collection of Micro-organism Cultures of the INSTITUT PASTEUR of Paris 28 rue du Docteur Roux, 75724 Paris Cedex 15, under numbers I-232, I-240 and I-241. Morphologically and immunologically similar virus strains have been isolated in other laboratories; the retrovirus strain HTLV-III (Gallo et al., Science, 224, 500 (1984); Sarngadharan et al., Science 224, 506 (1984); and ARV, isolated by Levy et al., Science, 225, 840-842 (1984). Reference is also made to European patent application filed Sep. 14, 1984, with the priority of British patent application number 83 24800, filed Sep. 15, 1983, which corresponds to U.S. Ser. No. 558,109, filed Dec. 5, 1983, now abandoned, as regards a more detailed description of the LAV retroviruses and uses of extracts of these viruses.
Only the core antigens of the virus could be recognized, after lysis of the virus, by sera of patients infected with AIDS or LAS. A protein p41 has been described in the above articles on HTLV3 as a possible component of the envelope of the virus. However, formal proof that p41 was a protein of the envelope has not been forthcoming.
Processes for obtaining a LAV virus or a related virus have also been described. Barre-Sinoussi et al., cited above, describes the preparation of the virus in T lymphocyte cultures derived either from blood, or from the umbilical cord, or from bone marrow cells of adult donors in good health. This process comprises particularly the following essential steps:
viral infection of the T lymphocytes, after activation by a mitogenic lectin, with a viral suspension derived from a crude supernatant liquor of lymphocytes producing the virus (initially obtained from a patient infected with AIDS or LAS), PA1 culturing of cells infected with TCGF, in the presence of anti-.alpha.-interferon sheep serum, PA1 purification of the virus produced (production commences generally the 9th and the 15th day following the infection and lasts 10 to 15 days) by precipitation of the virus in polyethyleneglycol to produce a concentrated sample of the virus, then centrifuging the preparation in a sucrose gradient of 20 to 60% or in isotonic gradient of metrozanide (sold under the trademark NYEGAARD.TM. by NYEGAARD, Oslo). The virus is then recovered with a strip of suitable density 1.16-1.17 in the case of the sucrose gradient or 1.10-1.11 in a NYCODENZ.TM. gradient.
The LAV virus may also be produced from continuous cell lines of type T, such as the CFM cell line, or from B lymphoblastoid cell lines, such as obtained by the transformation of the lymphocytes derived from a healthy donor with the Epstein-Barr virus. The cell lines obtained continuously produce a virus (LAV-B) which possesses the essential antigenic and morphological lines of the LAV viruses (except that it is collected in a strip of density sometimes slightly higher than in the preceding case, particularly 1.18) in sucrose. The final purification of the virus can also be carried out in a NYCODENZ.TM. gradient. Reference can also be made to general techniques of producing virus type B-LAV, French patent application, 84 07151, filed May 9, 1984.